Traffic control system



NOV. l, 1938. A. P. B RENSHAW ET AL 2,135,472

TRAFFIC CONTROL SYSTEM Filed May 16. 193s 5 sheets-sheet 1 B l dum/mfg, A30-rw 7g2-v6 ATTORNEYS.

NOV. l, A P B, RENSHAW ET AL 2,135,472

TRAFFIC CONTROL SYSTEM Filed May 16, 1936 5 Sheets-Sheet 2 Nov. l, 1938. A. P. B. RENsHAw ET A1. 2,135,472

TRAFFIC CONTROL SYSTEM Filed May 16., 193e 5 Sheets-Sheet 3 ATTORNEYS.

YPatented Nov. 1, 193.8

l UNITEDI STATES PATENT OFFICE TRAFFIC CONTROL SYSTEM Alfred Percy Bailey Renshaw, Kingston Hill, and Thomas Philip Preist, Roby, near Liverpool, England, assignors, by mesne assignments, to Automatic Telephone & Electric Company Limited, London, England Application May 16, 1936, Serial No. 80,056 In Great Britain May 21, 1935 k11 claims. (C1. 177-337) rThe present invention relates to traffic control in connection with the accompanying sheets of signals for use at road junctions or the like and drawings in Which:

`is more particularly ,concerned with systems in Figure 1 is a circuit diagram for one form of a which the period of display of the appropriate tra'ic controlr system embodying the invention 5; signals is controlled by traffic detectors located and comprising signal lights, signal controller or 5 in one or moreof the various traine lanes. In timer, and trail-lc actuatable detectors. one well-known system of this type it is arranged Figures 2 and 3 are each diagrams for alternathat when a vehicle actuates a detector, it setive forms of the system of Figure 1 in which cures to itself right of rway for a period suiifewer'parts are required in the signal controller cient to enable it to clear the crossing and acbut the facilities for the adjustment of timed 10 cordingly if vehicles follow each other suiciently intervals are not as complete as in the arrangeclosely right of way may be repeatedly extended. ment of Figure l.

However, in order that vehicles on an intersect- Referring now to Figure l, there is illustrated ing road shall not be unduly held up, separate a controller of the type now well known suit.- maximum timing means are provided to set a able fOr a Straight fOrWard right-angled ClOSSing 15 limit to the time during which one road can hold in Which a number 0f Contact Springs are 0P- right of Way if traine is waiting on an intersecterated by a cam shaft which is rotated step by ing road.v step by means of a solenoid. The solenoid is Traino control systems operating on this prinoperated at suitable intervals which are deterciple give good results in practice but a difficulty mined by the time taken t0 Charge a Condenser 20 sometimes arises in that owing to irregularities through a high resistance until it attains the in traftic lowright of way may be lost during striking Voltage ot a neon or similar gas discomparatively small gaps in an otherwise concharge tube whereupon the tube flashes and a tinucus stream of traffic unless the vehicle exrelay in Series therewith iS Operated 150y bring A tension period is sensibly increased. If this is about the' advance of the cam shaft to the next 25 done however, it means that each vehicle genposition. eratesan extension period in excess of its actual The arrangement sho-Wn. makes use Of the individual requirements and accordingly the time Well known arrangement 0f W timing Circuits, right of way is held by any particular road cannot One cf Which S Controlled from the Vehicle dctol be stn'ouy proportioned to the density of the tectors so that if tralcltcoltinvlestko` arrive 0n 3o traflic flow thereon. This limitation is of little the Toad possessing rig 0 Way e con ensei' consequence in circumstances where the traic is ntermttenty discharged and thus, an ex" densities on the respective roads are substantension of the mgm of Way perlods Obta'medg In tially constant because the required distribution Order however that me road may n.01? hold nght of right of way can be secured independently by 0f Way md-'emtely 1f @rame 1s Waltmg 0n the 35 a suitable setting of the maximum timing Otel rogi lsecom tlmmg @mgmt ii povgield switches, but in cases where there is an apan m s e, con enger 1S C arge s ea y preciable variation in the traffic density, better and cannot' be dlscharged by further Operations distribution than can be obtained by this method of the detector.' Consequntly l? a dfitector has 40 is desirable. The chief object of the invention eeierarlbelfpg ri; lsrcworzhti; jrfli 40 nenn enterrement fr Een a maximum to a ractice without an a reciable com lication' Vehicle thereon will have to Wait' In the ar' p .y pp. p rangement illustrated in Figure l the improved of the usgalcontmumg @q mpnnfent' working according to the invention is attained 45 Accordlng to the mvetmotl n.1 a" tramo Control by the provision of a third timing circuit which System arranged' to maman? mgm of way to a controls the operation of the second timing cirtfafcf lane/ s long as detecl'or Operations O ccur cuit by varying the resistance connected in the tnerem at mbwals of less tfhan a' prfdetermmed charging circuit of the condenser of the second value but subJect to a maximum period 1f trallc timing circuit' 50 lfll an intersecting lage fis Yequ rlght 0f Way Considering now the detailed operation of the e maXmuID perO 01 a ra c an@ S 211- circuits shown in Figure l it is assumed that the ranged t0 be Variable in accordance With the controller is fed from alternating current mains density of traiiic in that lane. connected to the transformer TR which is con- 55,v The invention will be described and explained veniently provided with suitable tapping points detector circuits.

to suit different line voltages. From the outer secondary windings of this transformer the valve rectifier VR is fed and this supplies direct current to the terminals marked plus and minus in a square, suitable smoothing devices being employed. From the terminals P and J of the Iniddle secondary winding alternating current of a suitable low voltage is obtainable for use inthe, Normally one side of the line, as the minus side, will be connected to ground. The terminals marked T are provided for convenience in testing.

The table at the right side of Figure 1 shows by a black circle or bar the shaft positions in `which the various cam contacts are closed. It will later be apparent from the description that in the absence of traffic the shaft will be standing in phase AA or phase B. Y For the purpose of description it will be assumed that the shaft is standing in position 3' giving right of way to phase A. Traffic now arriving on this road will operate the detector DA and hence, through the circuit from terminal P via relay D and detector DA to terminal J, will operate the relay D intermittently and this relay at armature d2 will shunt the condenser QA by resistance YD each time the relay is operated since cam contacts CIG are closed. The charging circuit for this condenser is completed from positive over cam contacts CI5- and the phase A vehicle interval adjusting switch VA which is suitably wired to the tappings of the common resistance AR' and charging of condenser QA proceeds between actuations of relay D by vehi-V cles on phase Af If Aa vehicle now appears on phase B it 'will-operate detector DB and energize relay E which'locks up at armature el. Moreover at armature e3 a circuit is completed over cam contactsl C8 and armature cl for relay F which is accordingly operated. Also the neon tube FA and relay A are connected by way of armature e2 and contacts CIT across the condenser QA so that if the potential of the condenser rises suiciently to reach the striking voltage of FA then relay A is operated by discharge of the condenser through this tube and relay.`

Assuming fo-r the moment that the condenser potential has not risen to the striking voltage, then also by relay E at armature e4 a charging circuit is completed by way of cam contacts CIZ, operated armature f2, the maximum adjusting switch MA andthe common resistance BR for thecondenser QB, and also a branch charging circuit is supplied through armature e4 over armature f3 and the density timing adjusting switch DTA and common resistance CR for condenser QC. In consequence of the operation of armature e5, each time that relay D is operated by further traffic on phase @condenser `QC is shunted at armature d5 over resistance YE. 'I'he adjustment of the various switches is such how-V ever that condenser QC rwill attain the striking voltage of the tube FC before condenser QA will attain the striking voltage of the tube FA. Y

Accordingly, if the trafc is heavy on phase A so that both condensers QA and QC are maintained substantially discharged, relay F remains energized and the maximum period, i. e. the time required to charge condenser QB to thestriking voltage of the lamp FB, is determined by the setting of the maximum adjusting switch MA. If, however, the density of traffic on phase A falls off so that condenser QC is enabled to reach the striking voltage of tube FC, relay C is operated by winding CI and at armature cl opens the circuit of relay F and at armature c2 completes a locking circuit for itself by way of con'- densers Q, its winding C2, armature a2 and armature d3.y The rectifier MRC is provided in order to give' reliable operation of relay C' which is. ofthe directrcurrent type. In view of the release of relay F the charging resistance in the maximum` timing circuit is nowrconnected up over the back contact of armature f2 and the reduced maximum adjusting switch MRA which is wired to the same resistance BR but is set to give a more rapid charging effect. Moreover'at armature-f3 the chargingcircuit for the density timing circuit is opened. If further traffic arrives on phase A before the operation of either relay A or relay B, relay D is again energized and at armature* d3 opens the locking circuit of relay C which therefore de-energizes and again connects up relay F whereuponY the conditions previously described are restored.

"Assuming that there is eventually a gap in the phase -A'trailic sufficient to enable condenser QA to charge up to the striking voltage of tube FA thuscausing relay A to operate, relay A at arma.- ture al then completes the circuit of the solenoid S and at armature a2'ope'ns the locking circuit of relay C which will necessarily be energized at the time. The solenoid now advances the cam shaft into ,position 4 and at its contacts sl, s2 and s3 shunts condensers QA, QB and QC by resistances YA, YB, and YC respectively, so as toV rensure that they shall start the next timing period with substantially no residual charge. In position 4 cam contacts C2 are closed and the charging circuit for condenser QA therefore extends over the amber adjusting switch LA. If the stepping of the cam shaft had been brought about by relay B due to the striking of maximum circuit neon tube FB, armature b2 and solenoid contacts S4 would be operated to ensure that relay YD still remained energized over its clocking `circuit viaV dl and Cl for retransferring right of way to the A phase at the earliest o-pportunity, and consequently the charging circuit would now include Y resistance YF which gives an extended'amber period to@ give time for theV crossing to clear..

The continued energization of relay D ensures that right o-f way shall return to phase A without any further detector operation so as tore ylease any vehicles` which may have been stopped.

If relay D is not operated .however resistance YF is short-circuited by contact d4 and the amber period is correspondingly shortened. It will be appreciated that some degree of extension is obtained if the detector DA is crossed by a Vehicle during the amber period.

When condenser QA has reached the striking voltage of tube FA, the tube flashes and relay A in series with the tube is energized momentarily. Relay A at contact al causes solenoid S to operate and advances the cam shaft to position 5.

When the cam (shaft is in position 5, charging takes place over cam contacts C3 .and the initial interval adjusting switch IB and at the end of It will be understood that the signallingV lamps GB, RA, GA, AB, and vRB are operated over cam contacts C9, CIU, CII, C20, C2i and C22 respectively in a manner which will be readil'y followed from the cam contact operation table at the right of Fig. 1. When the switch I-I is closed a connection is established between the amber lamps AA and AB vto give an amber indication with the red indication immediately prior to the change togreen as well as following the green.

The switches PA and PB associated with the detector circuits are so-called arterial switches and the throwing of a switch will ensure that right of way will return to the associated phase in the absence of traflic on the -other phase. The effect of these switches is to put in a call but not to produce any extension in the absence of traiiic. The terminal PH may be connected to a push button to enable stepping of the solenoid to be 4effected manually. f

It may be mentioned that with the circuit as shown in Figure 1,2traffic on the phasek possessing right of way will exert some additional control on the density timing circuit over the opposite density timing switch. This effect however, only loccurs during actual vdetector operation and is not found to produce any objectionable eifect since resistance YE is low enough to discharge condenser QC substantially completely each time relays D and E are operated together.

The signal control system of Figure 2 is lgenerally similar to that shown in Figure 1 in function and construction but has the following differences. Condenser QC, together with its charging circuit over contacts f3 and f4, switches DTA and DTB. resistance CR, are omitted from Figure 2, and the neon tube FC and winding: Cl'of its cooperating relay C are now connected directly across condenser QA. It is-necessary in this case forthe tube FCto strike at an appreciably lower voltage than the tube FA. With this circuit arrangement the dischar-ge circuits thru resistor YC and contact s3 and thru resistor YE and contacts d5 and e5 may also be omitted. The arrangement shown in Figure 2, however, does not give such complete facilities for adjustment as that of Figure 1.

The arrangement of the system in Fig. 2 operates through its cycle in the same general manner as that of Fig. 1, condenser QA being charged over the resistance AR and the appropriate adjusting switch and cam contact in each of the several positions of the camshaft, and upon the .potential onv condenser QA reaching the striking voltage of tube FA, the condenser discharges through tube FA to operate relay A, and in turn the solenoid S, to step the camshaft to the next position, all as described in connection with Fig. 1. As in Fig. 1,'in positions 3 and 6 of the shaft,V vehicles arriving on the phase having the right of way will momentarily discharge condenser QA and thus delay it in reaching the striking voltage of tube FA and so prolong the time the shaft remains in such position and the time of right of way on such phase. This prolongation is limited by the maximum timing unit including condenser QB, the associated charging circuits over resistance BR and appropriate maximum time adjusting switch and cam contact,l and the tube FB and relay B which are operated where condenser QB is charged vto the striking potential of tube FB to operate solenoid S, as described in connection With Fig. 1. f

Further in Fig. 1 the charging time of the maximum timing condenser QB is reduced by de-energizing relay F through energization of relay C, but the means for energizing relay C is somewhat different. In Fig. 2, tube FC and relay coil CI, as well as tube FA and relay A, are connected across condenser QA. Assuming the camshaft to be in position 3 for example, the condenser QA will be charged gradually between actuations of relay D by vehicles on phase A, and if a vehicle is waiting on phase B relay E will be maintained operated and relay F will be energized. Tube FC has a considerably lower striking voltage than tube FA and as condenser QA is charged, if the vtime is sufficient between vehicle actuati-ons on phase A, the striking potential of tube FC will be reached rst, the tube will ignite and suiiicient current will flow from condenser QA -through relay coil CI to energize the relay, and the relay will lock up over its second coil C2 and associated contact c2 as in Fig. 1. The yimpedance of the circuit through relay coil Cl is suflicient in relation to the charging resistance AR, with appropriate capacity of condenser QA, so that condenser QA can continue to charge to the striking voltage of tube FA if suicient further time elapses before another vehicle actuation on phase A. When relay C is energized relay F is de-energized as in Fig. 1, and if another A phase vehicle actuation occurs, energizing .relay D, then relay C will be cle-energized and relay F re-energized as in Fig. 1. It will thus be observed that Fig. 2 differs from Fig. 1 only in vthe arrangement for energizing relay C.

A further alternative arrangement which does not involve the use of a third neon tube, is shown in Figure 3. Herein the maximum timing condenser QB is arranged to be partially discharged by traffic in the road possessing right of way. Accordingly an actuation of detector DA while right of way is on the A phase with the ycontroller in position 3, would by its momentary operation of relay D cause condenser QB to be partially discharged over contacts d5, cam kcontacts C8, closed in shaft position 3, and resistor YH. Similarly in the B phase vehicle interval position 6, actuations of detector DB cause QB to be discharged over contacts e6. In this arrangement the resistance BR in the maximum period charging circuit is set at a comparatively low value while the discharge resistance YH is suiciently high so that it cannot prevent the striking of the tube FB if a detector were operated continuously. Thus the partial discharging of the condenser through resistor YH does not reduce the charge on the condenser but reduces the rate of charging, by shunting oir a part of 'the current flowing through charging resistance BR. This embodiment of the controller eliminates tube FC, relays C and F, contacts e3, d3 and adjusting switches MRA, MRE of the Figure 2 device.

If desired the make-before-break type of contacts e6, d6, in Fi-gure 3 may be replaced by ordinary make type contacts when used in conjunction with cam contacts C8 and C19, or if the make-break contacts are retained, cam contacts C8 and Ci9 may be omitted. In the latter case, where the make-break type contacts are used, the period of contact closure is independent of the length of time the detector is operated, and accordingly satisfactory operation may-be obtained without cam contacts C8 and C19, allowing the shuntingof 'the condenser QB to be produced at any time by operation of either of the road relays. f

The invention therefore by means of a simple addition to a system of known type and proved reliability provides a renement which makes the system more efficient in avoiding congestion and facilitating the free ow of traic With the minimum of delay. Y

While in the foregoing description several modifications of the invention and their method ofapplication to a form of traffic control system have been illustrated it will be apparent to those skilled in theart that the invention may take many forms, and it is not to be construed that the invention is limited to these particular embodiments. Further it will be appreciated that numerous changes in construction or rearrangement of the parts might be made Without departing from the spirit of the invention as deiined in the claims.

We claim;

1. A traffic control system arranged to control right of way in a traiiic lane and including in combination. traiic actuated means in the lane, a control mechanism for according right of Way to and transferring right of way from said lane, said mechanism including timing means for maintaining right of way in said lane for at least a minimum and up to a maximum period in response to successive operations of said traffic actuated means occurring during accord of right of way to said lane, and spaced from each other within a predetermined time interval, a timing device included in said control mechanism to measure a time interval less than said predetermined time interval and beginning from each of such operations of the traflic actuated means, and means operating upon completion of its time yinterval by said timing device to reduce said maximum period of said timing means.

2. A trafc control system for the control of right of way on intersecting traino lanes including in combination, traic actuated means in one of said lanes, a control mechanism for according right of way to and transferring right of way between said lanes, said mechanism including three timin-g devices for controlling the time of accord and transfer of right of Way by said mechanism, one of said timing devices for timing the intervals between successive operations of the traino actuated means by traffic in said one lane occurring while right of way is accorded to said one lane and for initiating transfer of right of Way to another of said lanes by said control mechanism in response to operation of the traiic actuated means in said another lane and only'if such intervals between successive operations exceeds a predetermined value, and a second of said devices to provide a maximum time limit to right of way in said one lane and,V

to initiate transfer of right of way to said another lane if right of way is accorded in said one lane up to such limit, and the third of such debetween said lanes, said mechanism including three timing devices for controlling the time of accord and transfer of right of way by said mechanism, at least the first and third of which devices each comprise a condenser, means for varying the charge on lthe condenser from an initial value to a final value and means operating responsive to the final value of char-ge on said condenser to indicate the completion of the time interval of the time'device, one of said devices adapted to operate while right of way is accorded to said one lane to control the time of right of Way in said one lane and including means connected between said traic actuated means and said condenser to reset the charge on said condenser substantially to said initial value by each operation of said trac actuated means to maintain right of Way in said lane for a longer time and also including means to initiate transfer of right of Way to another laneif said charge responsive means so operates at the completion;

of its time interval, a second of said devices adaptedto operate While right of way is accorded to said oneflane to provide a maximum time limit beyond which right of way cannot be maintained in said lane by successive reset of the first timing device by traic and including means to, initiate transfer of right of way toV said another lane if right of way is maintained up to such limit, and the third timing vdevice adapted to operate While right of Way is accorded to said one lane and also including means for resetting the charge on its condenser substantially to'said initial Value in response to each such operation of said traffic actuated means so as to time a certain interval beginning from each such operation, and means operated by operation of the charge responsive means of said third timing device to reduce the time limit of said secondV Y timing device. 4. A traffic control systemas claimed in clai 3 in which one condenser is common to the rst and third timing devices and in which the charge responsive means of said first and third timing 6. A traffic control system to control right `of Way in a traffic lane and including in'combination, traffic actuated means in said lane, a control mechanism for according right of Way to Vand transferring right of way from said lane,Y

said mechanism including. a timing device for maintaining right of way in said lane in response to successive operations in said traflic actuated means occurring during accord of Vright of way to said lane, and spaced from each other Within a predetermined time' interval, a second timingV device to provide a maximum time limit to right of Way inv said Ylane and to initiate transfer of right of Way from said lane if right of Way is accorded to said lane up to such limit, said second timingdevice comprising a condenser Vand means including a resistance for varying the charge on said condenser from an initial to a final value and means operating responsiverto said nal value of charge on said condenser to complete said maximum time limit and initiate such transfer of right of way, and means in said control mechanism and operated by said traffic actuated means to partially counteract, by each operation of the trafc actuated means, the varying of the charge on said condenser toward said c nal value whereby frequent operations of said trac actuated means will prolong said maximum period.

7. A traffic control system for the intersection of interfering trafc lanes and including in combination traflic actuated means in each of said lanes, means for according and maintaining right yof way in one of said lanes as long as the traic actuated means in said one lane isactuated by trailic successively at time intervals of less than a predetermined value, means operable upon an intervening actuation of the traiilc actuated means in a second of said lanes to prevent such maintaining of right of Way to said one lane beyond a maximum period beginning from the time of said second lane actuation, and means for decreasing said maximum period in response to the time spacing between successive actuations of the traic actuated means in the said one lane exceeding a time period of shorter predetermined value than said rst mentioned predetermined value but not exceeding the said mentioned predetermined value.

8. A traic control system as in claim 7 and including means for increasing said maximum period again by another successive traffic actuation occurring at a time interval of more than said shorter value but less than said first mentioned predetermined value from the last previous actuation.

9,. A traffic control system for the intersection of interfering traffic lanes and including in combination, tralic actuated means in each of said lanes, control means for according right of way to and transferring right of way between said lanes, said control means including a timing device for maintaining right of way in one of said lanes in response toI operations of the traine actuated means in said one lane during accord of l right of way to 'said one lane and spaced from each other within a predetermined time interval, other means forming a part of said control means and started in operation by an actuation of the traiic intervening actuated means in a second of said lanes to prevent such maintaining of right of way to said one lane beyond a maximum period from the time of said second lane actuation, another timing device included in said control means to measure a time interval less than said predetermined time interval beginning from each of said successive operations of the trail'c actuated means in said one lane, and means operating upon completion of the time interval by l said lastnamed timing device to reduce said maximum period.

10. A traic control system for the control of right of way at the intersection of interfering traic lanes including in combination traiic actuated means in each of said lanes, a control mechanism for according right of way to and transferring right of way between said lanes, said mechanism including three timing devices, one of said timing devices adapted to maintain right of way and time the intervals between successive operations of the traffic actuated means in one lane by traic therein while right of way is accoided to said one lane and to initiate transfer of right of way to a second lane only if such intervals exceed a predetermined value, a second of said devices started in operation by an intervening actuation of the traffic actuated means in said second lane to provide a maximum time limit to right of way in said one lane and to initiate transfer of right of Way to said second lane if right of Way is maintained in said one lane up to such limit, and the third of such devices adapted to time a certain time interval beginning from each of said successive operations of said traffic actuated means in said one lane and to reduce said time limit of said second device if the time interval between such successive operations exceeds said certain time interval but does not exceed said predetermined value.

11. A traiic control system for control of right of Way at the intersection of interfering trafc lanes and including in combination, trafc actuated means in the lanes, a control mechanism for according right of Way to and trarferring right of way between said lanes, said mechanism including a timing device for timing the intervals between successive operations of traic actuated means in one lane While right of way is accorded to said one lane and to initiate transfer of right of way to a second of said lanes by said mechanism only if such intervals exceed a predetermined value, a second timing device for providing a maximum time limit to right of way in said one lane and comprisinga condenser, means including a resistance for varying the charge on said condenser from an initial value to a final value over a time period corresponding to such time limit, and means operating responsive to the charge on said condenser reaching said final value to complete said time limit and to initiate transfer of right of Way to said second lane by said mechanism if right of way is accorded to said one lane until said condenser reaches said final value of charge, relay means energized during accord of right of way to said one lane and providing a certain value of such resistance in said charge varying means, said relay means operable when deenergized to provide a different value of such resistance for increasing the rate of varying of the charge by said charge varying means to decrease the maximum time limit, and a third timing device adapted to time a certain time interval beginning from each of said successive operations of said traffic actuated means in said one lane and to deenergize said relay means if the time interval between such successive actuations exceeds said certain time interval.

ALFRED PERCY BAILEY RENSHAW. THOMAS PHILIP PREIST.

CERTIFICATE 0E CORRECTION.,

Patent No. 2,l55,) 72. November l, 1958.

ALFRED PERCY BAILEY RENsHAw, ET AL.,

It is hereby certified that error appears ,in the printed specification offthe abovenumb ered-patent requiring correction as follows: Page 2, second .column,line )45, "gfor v"clocking" read locking; page 5, first column, line 51,' claim 9, strike out the word "intervening" and insert the same before "actuationi',z line 50, same claim; and that the said Letters Patent should be readwith this correction therein that the same mayconfom to the record of the lcase in thel Patent Office.

Signed and sealed this lith day of January, A. D. 1959."

Henry Van Arsdale (Seal) Acting Commissioner of Patents. 

